The invention relates to a method and a device for detecting a potential collision object in an image, which image is acquired by an imaging unit arranged in a motor vehicle, the imaging unit being designed for providing a digital source image of a predefined image size as a function of the acquired image. The invention further relates to a detection system for a motor vehicle.
When driving at night, a driver's visual range is essentially determined by an illumination of the road by means of front headlights of the vehicle, in which case night vision is frequently temporarily impaired by glare of front headlights of oncoming vehicles. Furthermore, many drivers partially lose their visual function at night. Motor vehicles are therefore increasingly equipped with night vision systems. Night vision systems are typically classified either as passive night vision systems or as active night vision systems. Passive night vision systems acquire infrared ambient light that is emitted by objects. Active systems use, for example, an infrared light source in order to illuminate a predefined area in the forward direction of the vehicle, and process an infrared light reflected by the objects by way of a special camera to form a thermal image. In the predominant number of cases, the acquired thermal images are displayed by a visual output unit, such as a display arranged in the instrument panel, or a head-up display.
It is an object of the invention to provide a method and a device for detecting a potential collision object, as well as a detection system for a motor vehicle, which permit a reliable detection of the potential collision object under various driving and/or traffic conditions for the motor vehicle and contribute to reducing an accident probability of traffic participants.
This and other objects are achieved by a method for detecting a potential collision object in an image, which is acquired by an imaging unit arranged in a motor vehicle. The imaging unit is designed for providing a digital source image of a predefined image size as a function of the acquired image. A first intermediate image of a predefined first intermediate image size is generated by reducing a resolution of the source image for the sake of reducing pixels. A second intermediate image of the predefined image size is generated such that it comprises the first intermediate image. The second intermediate image is analyzed by a predefined detector in order to examine whether an object of a predefined object category is situated in the second intermediate image. The detector is designed for analyzing a predefined image detail and for detecting an object of a predefined object category of a predefined object size range.
According to first and second aspects, the invention is characterized by a method and a corresponding device, for detecting a potential collision object in an image which is acquired by an imaging unit arranged in a motor vehicle. The imaging unit is designed for providing, as a function of the acquired image, a digital source image of a predefined image size. A first intermediate image of a predefined first intermediate image size is generated by reducing a resolution of the source image for the sake of reducing pixels. Furthermore, a second intermediate image of the predefined image size is generated such that it comprises the first intermediate image. The second intermediate image is analyzed by a predefined detector in order to examine whether an object of a predefined object category is situated in the second intermediate image, the detector being designed for analyzing a predefined image detail and for detecting an object of a predefined object category of a predefined object size range.
Within the scope of the invention, a size of a digital image, of a detail of the digital image or of an object in the digital image, is a horizontal and vertical dimension of the digital image, of the detail or of the object within an image plane measured by a number of pixels.
The detector includes, for example, in each case, a descriptor and a classifier that is applied to the descriptor. Here, the descriptor characterizes a characteristic or a group of characteristics in the image detail. By use of the classifier, for example, a confidence interval and/or a probability of a presence of the object in the respective image detail can be determined, and/or a decision can be made as to whether or not the object is contained in the respective image detail. For detecting the object of the predefined object category, the detector is trained, for example, by way of a plurality of example data. This training of the detector may therefore require very high expenditures. A detection performance of the detector may be a function of an object size of the object to be detected. The detector is therefore trained, for example, in such a manner that it reliably detects the object of the predefined object category in an application-specific object size range.
The reduction of the resolution of the source image allows an analysis by means of scaling of the image acquired by the imaging unit, so that the object of the predefined object category may have an object size that may be in the object size range in which the detector can reliably detect the object. An adaptation of the detector, which would otherwise be necessary for a reliable detection of the object in the source image by way of the detector, will not be required. Advantageously, a minimal detection distance, i.e. a minimal distance between a real object and the imaging unit, up to which the object can be reliably detected as a potential collision object, can therefore be predefined as a function of a scaling of the source image.
Advantageously, the second intermediate image has the image size which the source image also has, so that an analysis of the second intermediate image can take place by way of an appropriately designed program routine, which can also be utilized for the analysis of the source image by the predefined detector.
In an advantageous further development, when the object is detected in the second intermediate image, the object can be classified as a potential collision object as a function of a distance of the motor vehicle from the object and/or of a speed of the motor vehicle, and a signal is generated for signaling a predefined warning. This makes it possible to draw the vehicle user's, particularly the driver's, attention to a danger in sufficient time, so that the driver and/or the vehicle can appropriately react for avoiding a collision. The warning may, for example, be signaled by means of an acoustic signal, a visual signal, and/or a haptic signal.
In an advantageous further development, a first pixel value is determined as a function of pixel values of the source image or of the first intermediate image, and remaining pixels of the second intermediate image, which are not comprised by the first intermediate image, have the first pixel value.
In a further advantageous development, the first pixel value is representative of an average value of approximately all pixel values of the source image or of the first intermediate image. This permits a simple and fast determination of the second intermediate image.
In a further advantageous development, the imaging unit is designed for acquiring a thermal image. The imaging unit may, for example, comprise an infrared camera. This advantageously makes it possible that heat-radiating objects, for example, living beings, can be detected especially at night. The predefined object category may comprise specific types of animals and/or persons for this purpose.
In a further advantageous development, the predefined object category comprises predefined types of animals, pedestrians and/or bicyclists who are situated and/or are moving in the edge area of a road and/or on a road, on which the motor vehicle is driving. This makes it advantageously possible that predefined types of animals, pedestrians and/or bicyclists, who are situated and/or are moving in the edge area of the road or on the road, on which the motor vehicle is driving, can be recognized in time.
In a further advantageous development, the resolution of the source image is reduced by a subsampling of the source image. This permits a simple and fast determination of the first intermediate image.
In a further advantageous development, the first intermediate image size is by a predefined factor, which represents a square number, smaller than the image size of the source image. This permits a simple subsampling. Furthermore, a smooth filtering of the source image can be carried out in a very simple manner. For example, an average value can be determined, for example, an arithmetic average, of an image detail out of, for example, a width of 2 pixels and a height of 2 pixels, and this average value forms a new pixel of the first intermediate image. Thus, the smooth filtering and the subsampling can be carried out in one step.
According to a third aspect, the invention is characterized by a detection system for a motor vehicle. The detection system has an imaging unit arranged in the motor vehicle, which imaging unit is designed for providing, as a function of an imaged acquired by it, a digital source image of a predefined image size. Furthermore, the detection system comprises a device arranged in the motor vehicle according to the second aspect for detecting a potential collision object in the image acquired by the imaging unit. Advantageous further developments of the first and second aspect also apply to the third aspect.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.